A media object (such as a song, image, video, or other multimedia object), stored on a server and optimized for later playing on a mobile device can be delivered to the mobile device proactively or reactively. In proactive delivery, the media object is delivered to and stored on the mobile device ahead of when the user attempts to access it. In reactive delivery, the media object is held on the server until it is requested by user, and then streamed to the mobile device and played immediately.